JPS6214764B2 - - Google Patents

Description

Detailed Description of the Invention This invention provides, for example, a vortex generation column in the gas flowing in the air intake pipe of an automobile internal combustion engine, and detects the number of Karman vortices (vortex frequency) generated downstream of the column using ultrasonic waves. The present invention relates to a Karman vortex current meter that measures intake flow velocity or flow rate, and its purpose is to provide a method that can stably detect even weak vortices at low flow speeds.

A method was proposed in Utility Model Application Publication No. 51-24154, in which a vortex generation column is provided in a conduit, and the generation frequency of the Karman vortex generated downstream of the column is detected using ultrasonic waves to measure the flow velocity or flow rate of the fluid flowing inside the tube. ing. When detecting the Karman vortex using this method, the ultrasound transmitted from the ultrasound transmitter propagates through the fluid, is modulated by the Karman vortex, and is received by the receiver. The magnitude of the modulation caused by the vortex is determined by the strength of the vortex and the speed of sound. When the flow velocity of the fluid is low, the vortices become weaker, the degree of modulation becomes smaller, and the detection S/N ratio deteriorates. In the intake system of an internal combustion engine for automobiles, the temperature of the intake gas and the temperature of the current meter itself are affected by the heat generated by the internal combustion engine. As a result of the temperature difference between the flow rate and the flow rate, heat transfer from the current meter creates a temperature distribution in the inlet gas within the conduit. However, since the degree of modulation of a vortex is a function of the speed of sound, if there is a temperature distribution in the suction gas, the propagation speed of the ultrasonic wave passing through that gas layer, that is, the speed of sound, will differ, so the ultrasonic wave will not be modulated by the temperature distribution. I will receive it. Therefore, when the flow rate of the intake gas is low, that is, when the degree of modulation due to the vortex is small, the modulation component due to the temperature distribution of the intake gas becomes noise and the S/N decreases.
The ratio deteriorates further, making it difficult to stably detect only Karman vortices.

This invention eliminates the temperature distribution of the suction gas by stirring the suction gas or promoting heat exchange between the suction gas and the conduit of the current meter on the upstream side of the vortex generating column, thereby creating an air stream with a uniform temperature. By doing so, the present invention aims to provide a Karman vortex current meter suitable for the intake system of an automobile internal combustion engine, which can remove modulation components due to temperature distribution and stably detect only Karman vortices.

The embodiment shown in the figures will be described below. 1st
The figure is a sectional view showing an embodiment of the present invention. In the figure, 1 is a conduit through which the suction gas flows, 2 is a vortex generation column installed approximately perpendicular to the flow of the suction gas, 3 is a Karman vortex generated by the vortex generation column, 4 is an ultrasonic transmitter, and 5 is an ultrasonic transmitter. An ultrasonic receiver, 6 an ultrasonic wave, 7 a vortex detection circuit that detects a Karman vortex using a received signal modulated by a Karman vortex based on the drive signal of the ultrasonic transmitter 4; ,
The ultrasonic receiver 5 and the vortex detection circuit 7 constitute a vortex detection device. 8 is a self-propelled rotating axial flow fan arranged upstream of the vortex generating column 2; 9 is a suction gas fan; 10 is a suction gas fan 8 disposed downstream of the axial flow fan 8 and upstream of the vortex generating column 2; A fluid regulator 11 is an air cleaner disposed upstream of the conduit 1 and consists of a case 11a and a filter 11b.

In such a configuration, if a temperature distribution occurs in the intake gas 9 that has flowed into the air cleaner 11,
Alternatively, a temperature difference exists between the intake gas 9 and the air cleaner 11 or conduit 1, so that the gas flow 9
Even if a temperature distribution occurs in the vortex generation column 2
The suction gas 9 passing through is stirred by the axial fan 8 disposed upstream of the fluid regulating fluid 10, and is rectified by the fluid regulating fluid 10, resulting in a gas flow with uniform temperature. Therefore, the temperature of the Karman vortex 3 formed downstream of the vortex generating column 2 is kept constant regardless of the location, and when this Karman vortex 3 is detected by the ultrasonic wave 6, the modulation component due to the temperature distribution is ignored. As a result, only the modulation component due to the Karman vortex 3 can be measured, and as a result, the S/N ratio of the measurement is greatly improved, and there is an advantage that even weak Karman vortices at low flow speeds can be stably detected.

In the above embodiment, a self-propelled rotating axial flow fan was used as a means for stirring the gas, but the fan may be driven by an external force, or a rotating fin fixed within the conduit may be used. Similar effects can be expected. FIGS. 2a and 2b are block diagrams showing another embodiment of the present invention, in which reference numeral 12 indicates heat exchange fins attached around the conduit 1, and reference numeral 13 indicates the intake gas 9 between the heat exchange fins 12. It is an outer conduit that surrounds the conduit 1 so as to allow it to flow. In such a configuration, the temperature distribution of the intake gas 9 passing through the vortex generating column 2 is different from that of the heat exchange fin 1.
2, it is removed and homogenized by heat exchange. Further, since the heat exchange fins 12 have a rectifying function at the same time, there is an advantage that the rectifying effect of the flow regulating body 10 can be further enhanced.

As explained above, the present invention is capable of stabilizing Karman vortices even at low flow speeds by providing a simple means such as a stirring fan or a heat exchange fin to uniformize the temperature unevenness of the suction gas upstream of the vortex generating column. It has the effect of being able to be detected and improving the S/N ratio of measurement. In addition, since the temperature equalization means is provided upstream of the rectifier, even if turbulence occurs in the gas flow when equalizing temperature unevenness, it can be rectified by the downstream rectifier. A vortex can be generated stably.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the structure showing one embodiment of the invention, Fig. 2a is a cross-sectional view of the structure of another embodiment of the invention, and Fig. 2b is a cross-section taken along line bb in Fig. It is a diagram. In the figure, 1 is a conduit, 2 is a vortex generation column, 3 is a Karman vortex, 4 is an ultrasonic transmitter, 5 is an ultrasonic receiver, 6 is an ultrasonic wave, 7 is a vortex detection circuit, 8 is an axial fan, 9 is the intake gas, 10 is the fluid regulator, 11 is the air cleaner,
12 is a fin, and 13 is an outer conduit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A vortex generation column disposed inside a conduit substantially perpendicular to the gas flow, an ultrasonic vortex detection device for detecting the number of Karman vortices generated on the downstream side of this generation column, and the above-mentioned vortex. A Karman vortex current meter comprising: a rectifier provided upstream of a generation column; and means for equalizing gas temperature inside a conduit upstream of the rectifier. 2. The Karman vortex current meter according to claim 1, wherein the means for equalizing the gas temperature is constituted by means for stirring the gas on the upstream side of the rectifier. 3. The Karman vortex flow velocity according to claim 1, wherein the means for equalizing the gas temperature is constituted by an axial flow fan that is self-propelled and rotates by the incoming gas on the upstream side of the rectifier. Total. 4. The Karman vortex current meter according to claim 1, wherein the means for equalizing the gas temperature comprises forming a gas flow between a conduit provided with fins around the circumference and an outer wall surrounding the conduit.